In vitro production of conidia of Elsinoë ampelina, the causal fungus of grapevine anthracnose

Abstract

Anthracnose, caused by Elsinoe ampelina, is an important disease of grapevines in humid and warm production regions of the world. Colonies of E. ampelina grow slowly and rarely produce conidia on artificial media. To facilitate studies involving E. ampelina, our objective was to develop a method to induce significant conidial production of this fungus. In the present study, we induced the in vitro production of conidia of 10 Australian isolates by shake-incubation of mycelial fragments in rainwater under continuous light and darkness. Furthermore, seven Brazilian isolates were shake-incubated in rainwater and distilled water under continuous darkness. In both experiments cultures were shaken at 200-rpm and kept at room temperature (22–25 °C) for 7 days. Conidial production, germination, and severity of symptoms were quantified. Australian and Brazilian isolates produced different amounts of conidia. All Australian isolates sporulated in rainwater ranging from 4.20 × 103 to 5.91 × 106 conidia mL−1, with more than 90% conidial germination on water agar medium. All but one Brazilian isolate produced conidia in rainwater and distilled water, ranging from 7.50 × 103 to 8.22 × 106 conidia mL−1, with high germination percentages. Conidial suspensions from both Australian and Brazilian E. ampelina isolates caused typical anthracnose symptoms on grapevine leaves. This study describes an efficient method, using rainwater or distilled water associated with shaking, to induce the conidia production of E. ampelina.